Hmmm...what would you want of a "true sequel"?
I hear you but why fix something that isn't broken? SF 2 offers improved AI, that alone is reason enough to upgrade. Also, more missions that should be better designed, a better fleet management interface, 2 new races and that Dynaverse II which could be anything from quaint to totally gnarly. The beefed up visuals are icing on the cake.